Background: Salmonella, as an aerobic and facultative anaerobe bacillary gram-negative bacterium, is pathogen for humans and animals. This bacterium dominates the vertebral gastrointestinal tract, depending on the serotype and host conditions and factors, causes diseases with various symptoms and complications. Today, the development of multiple antibiotic resistance in this bacterium is a major barrier to public health. Integrons can play an important role in creating and expanding this resistance. The aim of this study was to investigate the presence of class I, 2 and 3 integrons in Salmonella typhimurium isolated of clinical samples by Multiplex PCR.Materials and methods: In this study, 60 isolates of Salmonella typhimurium were collected from Tehran Hospitals and confirmed by biochemical and culture tests. Multiplex-PCR assay was performed to identify int1, int2 and int3 integrons genes.Results: Of the 60 strains of Salmonella typhimurium, PCR assays detected 85% integron class 1, 45% integron class 2, and 70% integron class III.Conclusion: The results of this study showed high incontinence in Salmonella typhimurium strains isolated from clinical cases. Identifying these genes can be an important strategy in identifying and responding to antibiotic resistance, since the presence of infrared cells is an indicator of the development and spread of antibiotic resistance.